Meeting Abstract

43.3  Tuesday, Jan. 5  A New Look at the Evolution of Jumping in Frogs REILLY, S. M.*; JORGENSEN, M. E.; ESSNER, R. L. ; Ohio University reilly@ohio.edu

Frog jumping is one of the most enigmatic and paradoxical evolutionary transitions in vertebrate evolution. The current hypothesis for the evolution of jumping in frogs follows from the work of Emerson which proposed that the Anura possess 3 different iliosacral configurations that are correlated with locomotor mode, ecology, and phylogenetic groups as well. One configuration (with bowtie-like moderately expanded sacral diapophyses) is mostly a lateral bending system in walker/ hoppers and some burrowers. Another configuration (with greatly expanded sacral diapophyses) is predominantly a fore-aft sliding system in derived aquatic forms but is also scored for some climbing and burrowing forms. The third (with non-expanded diapophyses) is hypothesized to function as a sagittal-hinge, limiting the iliosacral movement to a vertical rotation and is related to long distance jumping. The correlation of the sagittal-hinge joint with long distance jumping (as in ranoid frogs) has led to the hypothesis that ranoid-like long distance jumping is the basal condition for anurans on the basis of scoring the most primitive living (Ascaphus) and extinct (Prosalirus) taxa as having the sagittal-hinge jumping system. New data from a re-examination of the pelvis in basal frogs shows that Ascaphus and Leiopelma, the two most primitive living frogs and all of the more basal living (Bombina, Discoglossus) and extinct species (with sufficient skeletal material) do not possess the characteristics of the sagittal-hinge iliosacral system well known in the ranoid frogs. This discovery leads to a new hypothesis that the transition from walking and hopping to sagittal-hinge jumping occurred well within the frog radiation rather than early in the evolution of frogs.